(Reuters) – A federal judge in Detroit on Tuesday declared unconstitutional a U.S. law banning female genital mutilation, and also dismissed several charges against two doctors and others in the first U.S. criminal case of its kind.

U.S. District Judge Bernard Friedman said Congress lacked authority under the Commerce Clause to adopt the 1996 law, and that the power to outlaw female genital mutilation, or FGM, belonged to individual states.

“As despicable as this practice may be, it is essentially a criminal assault,” Friedman wrote. “FGM is not part of a larger market and it has no demonstrated effect on interstate commerce. The Commerce Clause does not permit Congress to regulate a crime of this nature.”

Gina Balaya, a spokeswoman for U.S. Attorney Matthew Schneider in Detroit, said that office would review the decision before deciding whether to appeal.

The decision removed the main charges against Jumana Nagarwala, a doctor who performed the procedure on nine girls from Michigan, Illinois and Minnesota at another doctor’s clinic in the Detroit suburb of Livonia.

FGM is a religious custom performed on girls from her Muslim sect, the Dawoodi Bohra.